Under the Hood: Spec revision's cost is in the cards

As cdma2000 1xEV-DO Rev. A phones roll out in 2008, what impact will the new, higher-speed network have on the underlying platforms found in these handsets? The answer may lie in a comparison of Portelligent teardowns of two PC cards: the Release 0 Sierra Wireless 5220, launched at the beginning of the Sprint 1xEV-DO rollout, and the Rev. A Novatel EX720 Express Card 34, which was made available on the Sprint network in February 2007.

With maximum download speeds of 3.1 Mbits/second and upload speeds of 1.8 Mbits/s, the launch of cdma2000 1xEV-DO Rev. A in 2006 provided significant bandwidth improvement to the well-established 1xEV-DO Release 0 deployments. Although maximum speeds are rarely achieved in real-world settings, the new version of 1xEV-DO was expected to achieve at least a doubling of average download and upload speeds compared with Rel. 0.

Anxious to provide business laptop users with high-speed access to corporate networks, Sprint Nextel was the first cellular service provider to make the jump to the new technology, doing so in October 2006, but restricted the use of Rev. A to PC users with a network card. Since that time, many CDMA carriers have joined ranks with Sprint and upgraded their networks to Rev. A, although with limited handset availability. In late 2007, Rev. A phones from LG and Samsung were announced for the Korean market, and two Toshiba phones capable of taking advantage of the KDDI Rev. A network were made available in Japan. Sprint recently announced the first phone to take advantage of its Rev. A network through a ROM upgrade of the HTC Mogul, which has been available since June 2007.

Sierra Wireless 5220Based on a standard PCMCIA Type II, 68-pin card format, the Sierra Wireless 5220 provided PC users with maximum download speeds of 2.4 Mbits/s and average speeds of 300 to 600 kbits/s on the Sprint 1xEV-DO Rel. 0 network. Although not up to the average Wi-Fi and HSDPA speeds quoted today, the throughput enabled by Rel. 0 was 10 times faster than the dial-up modems found in many laptops available at the time of the 5220 launch.

The Sierra Wireless PC card was designed around a Qualcomm chip set that included an MSM5500 baseband processor, an RFR3300 RF-IF receive processor, two IFR3500 IF-baseband receive processors and a single RFT5600 transmit processor. The transmit path following the RFT5600 consisted of two Anadigics power amp modules. For interfacing with the PCMCIA Type II Connector, a two-port PCI-to-USB host controller by Transdimension and a USB interface by Philips Semiconductors (now NXP) were used. All components resided on a six-layer FR-4 pc board that filled the 54-mm x 117-mm PC card metal enclosure.

A search of Portelligent's product profile database revealed the first use of the MSM5500 platform in Korean CDMA multimedia phones, given that country's early rollout of the EV-DO network. With an ARM7 core and limited multimedia functionality integrated onto the digital baseband, the Korean phones required an additional processor to handle camera imaging, MP3 playback and video encoding/decoding. In another departure from the Sierra Wireless PC card, the Korean phones used a Qualcomm RFT3100 transmit processor along with either a Qualcomm IFR3500 or a Samsung S1M8662 receive processor.

Storing the communications software required a stacked memory package, which included a 4-Mbyte NOR flash from Advanced Micro Devices (Spansion) and a 1-Mbyte SRAM from Samsung Electronics.

Novatel EX720 ExpressCard 34Introduced nearly three years after the Sierra Wireless 5220, the Novatel EX720 ExpressCard 34 appeared to take advantage of expected die and package integration. The electronic components of the PC card were now able to fit in the new 26-pin, 34-mm-wide ExpressCard hardware standard. That standard, which was created in 2003 and is now common in many high-end notebooks, provides bandwidth of up to 2.5 Gbits/s, compared with the 132 Mbytes/s provided in the PCMCIA card standard. Other benefits beyond the smaller form factor and increased bandwidth are reduced power consumption, lower cost and better integration with the PC chip set.

Inside the Novatel EX720 enclosure was a 10-layer FR-4 pc board with a 40 percent reduction in board area over the board in the Sierra Wireless 5220. But the reduced area came at a cost, with the movement from a six-layer to a 10-layer board. Increased routing density, caused by the smaller board area and more I/O on the major ICs, forced the increase in layer count and drove a nearly 30 percent increase in the board's cost/cm2.

The core chip set found in the EX720 was built around the MSM6800 digital baseband, which was originally launched and sampled in April 2005 as Qualcomm's first product to support 1xEV-DO Rev. A. The MSM6800 was more than 50 percent larger in die area than the MSM5500 digital baseband used in the Sierra Wireless 5220, even though the 6800 was manufactured on a 0.13-micron process and the 5500 on 0.18 micron. Contributing to the increase in size was the MSM6800's use of a 225-MHz ARM926EJ-S core, two Qualcomm QDSP4000 DSPs, and hardware accelerators for video and gaming.

Future versions of the MSM6800 will benefit from TSMC's 65-nm process technology, with die sizes expected to be more than 60 percent smaller than for the 0.13-micron version.

Another component of the hardware platform affected by the transition to Rev. A was the memory, both in terms of capacity and die area. The memory requirement in the Novatel EX720 was satisfied by a stacked Samsung package consisting of 32-Mbyte NAND and 32-Mbyte low-power SDRAM. The increase in memory requirements resulted in a 50 percent increase in memory die area compared with the 5220. The increase was likely driven both by an increase in communication code size and by the transition from the more memory-efficient, execute-in-place memory architecture used in the Sierra Wireless 5220 to the store-and-download model found on the EX720.

Rounding out the Qualcomm platform in the EX720 was an analog baseband stacked with the digital baseband, power management provided by a Qualcomm PM6650, and radio functionality provided by an RFT6150 dual-band transmitter and RFR6500 diversity receiver. Supporting ICs included a set of Skyworks CDMA power amplifiers.

The transition from Rel. 0 to Rev. A of the cdma2000 1xEV-DO spec will afford mobile PC users and handset owners faster access to corporate networks and the Internet. The increase in bandwidth comes at a cost, however. The comparison of data cards highlights the requirement for more densely routed pc boards, faster and more full-featured processors, and increased amounts of memory. Overall, silicon area between the two devices grew about 30 percent with the latest iteration, albeit with lower total component count and tighter integration.

In the end, continuous advancement of semiconductor process technologies brings benefits of higher-speed networks in a cost structure simultaneously affordable to the consumer and profitable to both component and system manufacturers.

Jeff Brown is a principal analyst at Portelligent, a CMP company. The group produces teardown reports and related industry research on wireless, mobile and personal electronics (www.teardown.com).